The present invention relates to a material for silver complex diffusion transfer process and in particular to a negative material for silver complex diffusion transfer development.
In silver complex diffusion transfer process, in general a negative material comprising a support and a silver halide emulsion layer coated thereon, a positive material comprising a support and an image receiving layer containing physical development nuclei coated thereon and a processing solution containing a silver halide solvent are used.
That is, silver halide of exposed portion of exposed negative material is developed with a developing agent in the processing solution or the negative material (chemical development) and simultaneously silver halide of unexposed portion reacts with silver halide solvent to become a soluble silver complex salt, which diffuses into the positive material and is deposited at physical development nuclei of positive material (image receiving material) to form a silver image. In silver complex diffusion transfer process of this type, qualities of finally obtained image such as image density, color tone of image, contrast of image and storage stability of the obtained reproduced copy are important. A continuous tone original is reproduced on image receiving material for some uses, but higher contrast, sharpness and resolving power are required for using as a block copy for reproduction of documents, printed matter or for plate making. Furthermore, in the recent silver complex diffusion transfer development for higher transfer efficiency, namely, for completion of transfer in 5-15 seconds, it is necessary to obtain sufficient transfer density in a short time.
In one embodiment for carrying out silver complex diffusion transfer process as disclosed in British Patent Nos. 1,000,115, 1,012,476, 1,017,273 and 1,042,477, photosensitive silver halide emulsion layer or image receiving layer contains developing agent and hence processing solution used in development stage contains substantially no developing agent, namely, so-called alkali activation solution is used.
When such processing solution is used, the developing agent contained in the material must be contained in a large amount enough to be able to sufficiently develop exposed and unexposed silver halide.
U.S. Pat. No. 4,032,526 discloses to provide a photosensitive material for silver complex diffusion transfer which contains stably a large amount of developing agent by providing an antihalation undercoat layer containing a hydroxybenzene developing agent such as hydroquinone and a silver halide emulsion layer on a paper support coated with polyolefin resin on both sides with amount of hydrophilic colloid in the undercoat layer being larger than that in the emulsion layer.
Such photosensitive material for diffusion transfer process containing a developing agent is desired to be superior in permeability to alkali activated solution because chemical development in silver halide emulsion layer and physical development caused by diffusion of the developing agent in image receiving layer of positive material must proceed simultaneously. However, hydrophilic colloid (mainly gelation) undergoes change in properties due to the developing agent to inhibit hardening of hydrophilic colloid layer with hardener, resulting in the following defects: Permeability to alkali activated solution becomes too high and image reproducibility is deteriorated; If amount of hardener is increased for solving this problem, viscosity of coating solution increases or hardening gradually proceeds with lapse of time in storage of photosensitive material, and thus this results in reduction of maximum transfer density or reduction of contrast of image in running processing, namely, in processing with exausted alkali activation solution.
As attempt to improve the running processability, U.S. Pat. No. 4,632,896 has proposed a processing solution, but improvement in photosensitive material is also further required.